Glucocorticoid administration reduces cardiac dysfunction after brain death in pigs

Histological, Laboratorial, and Clinical Benefits of an Optimized Maintenance Strategy of a Potential Organ Donor-A Rabbit Experimental Model

INTRODUCTION

Most transplanted organs are obtained from brain-dead donors. Inflammation results in a higher rate of rejection. Objectives: The objective of this animal model of brain death (BD) was to evaluate the effect of the progressive institution of volume expansion, norepinephrine, and combined hormone therapy on clinical, laboratory, and histological aspects. Methods: Twenty rabbits were divided: A (control), B (induction of BD + infusion of crystalloid), C (BD + infusion of crystalloid and noradrenaline (NA)), and D (BD + infusion of crystalloid + vasopressin + levothyroxine + methylprednisolone + NA). The animals were monitored for four hours with consecutives analysis of vital signs and blood samples. The organs were evaluated by a pathologist. Results: In Group D, we observed fewer number and lesser volume of infusions (p = 0.032/0.014) when compared with groups B and C. Mean arterial pressure levels were higher in group D when compared with group B (p = 0.008). Group D had better glycemic control when compared with group C (p = 0.016). Sodium values were elevated in group B in relation to groups C and D (p = 0.021). In Group D, the organ perfusion was better. Conclusion: The optimized strategy of management of BD animals is associated with better hemodynamic, glycemic, and natremia control, besides reducing early signs of ischemia.

Excitation and contraction of cardiac muscle and coronary arteries of brain-dead pigs

Excitability and contraction of cardiac muscle from brain-dead donors critically influence the success of heart transplantation. Membrane physiology, Ca²⁺-handling, and force production of cardiac muscle and the contractile properties of coronary arteries were studied in hearts of brain-dead pigs. Cardiac muscle and vascular function after 12 h brain death (decapitation between C2 and C3) were compared with properties of fresh tissue. In both isolated cardiomyocytes (whole-cell patch clamp) and trabecular muscle (conventional microelectrodes), action potential duration was shorter in brain dead, compared to controls. Cellular shortening and Ca²⁺ transients were attenuated in the brain dead, and linked to lower mRNA expression of L-type calcium channels and a slightly lower I_Ca,_L, current, as well as to a lower expression of phospholamban. The current-voltage relationship and the current above the equilibrium potential of the inward K⁺ (I_K1) channel were altered in the brain-dead group, associated with lower mRNA expression of the Kir2.2 channel. Delayed K⁺ currents were detected (I_Kr, I_Ks) and were not different between groups. The transient outward K⁺ current (I_to) was not observed in the pig heart. Coronary arteries exhibited increased contractility and sensitivity to the thromboxane analogue (U46619), and unaltered endothelial relaxation. In conclusion, brain death involves changes in cardiac cellular excitation which might lower contractility after transplantation. Changes in the inward rectifier K⁺ channel can be associated with an increased risk for arrhythmia. Increased reactivity of coronary arteries may lead to increased risk of vascular spasm, although endothelial relaxant function was well preserved.

A standardized model of brain death, donor treatment, and lung transplantation for studies on organ preservation and reconditioning

BACKGROUND

We set a model of brain death, donor management, and lung transplantation for studies on lung preservation and reconditioning before transplantation.

METHODS

Ten pigs (39.7 ± 5.9 Kg) were investigated. Five animals underwent brain death and were treated as organ donors; the lungs were then procured and cold stored (Ischemia). Five recipients underwent left lung transplantation and post-reperfusion follow-up (Graft). Cardiorespiratory and metabolic parameters were collected. Lung gene expression of cytokines (tumor necrosis factor alpha (TNFα), interleukin-1 beta (IL-1β), interleukin-6 (IL-6), interferon gamma (IFNγ), high mobility group box-1 (HMGB-1)), chemokines (chemokine CC motif ligand-2 (CCL2-MCP-1), chemokine CXC motif ligand-10 (CXCL-10), interleukin-8 (IL-8)), and endothelial activation markers (endothelin-1 (EDN-1), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), selectin-E (SELE)) was assessed by real-time polymerase chain reaction (PCR).

RESULTS

Tachycardia and hypertension occurred during brain death induction; cardiac output rose, systemic vascular resistance dropped (P < 0.05), and diabetes insipidus occurred. Lung-protective ventilation strategy was applied: 9 h after brain death induction, PaO2 was 192 ± 12 mmHg at positive end-expiratory pressure (PEEP) 8.0 ± 1.8 cmH2O and FiO2 of 40%; wet-to-dry ratio (W/D) was 5.8 ± 0.5, and extravascular lung water (EVLW) was 359 ± 80 mL. Procured lungs were cold-stored for 471 ± 24 min (Ischemia) at the end of which W/D was 6.1 ± 0.9. Left lungs were transplanted and reperfused (warm ischemia 98 ± 14 min). Six hours after controlled reperfusion, PaO2 was 192 ± 23 mmHg (PEEP 8.7 ± 1.5 cmH2O, FiO2 40%), W/D was 5.6 ± 0.4, and EVLW was 366 ± 117 mL. Levels of IL-8 rose at the end of donor management (BD, P < 0.05); CCL2-MCP-1, IL-8, HMGB-1, and SELE were significantly altered after reperfusion (Graft, P < 0.05).

CONCLUSIONS

We have set a standardized, reproducible pig model resembling the entire process of organ donation that may be used as a platform to test in vivo and ex vivo strategies of donor lung optimization before transplantation.

Combined donor simvastatin and methylprednisolone treatment prevents ischemia-reperfusion injury in rat cardiac allografts through vasculoprotection and immunomodulation

BACKGROUND

Ischemia-reperfusion injury (IRI) and allograft dysfunction remain as two of the major clinical challenges after heart transplantation. Here, we investigated the effect of donor treatment with simvastatin and methylprednisolone on microvascular dysfunction and immunomodulation during IRI in rat cardiac allografts subjected to prolonged ischemia time.

METHODS

The DA rats received simvastatin, methylprednisolone, or both 2 hr before heart donation. The allografts were subjected to 4-hr hypothermic preservation and transplanted to the fully major histocompatibility complex-mismatched WF rat recipients.

RESULTS

Six hours after reperfusion, donor treatment either with simvastatin alone or with high dose of methylprednisolone alone or in combination with simvastatin and methylprednisolone significantly reduced cardiac troponin T release and the number of allograft infiltrating ED1 macrophages MPO neutrophils. However, the combination donor treatment was superior in the prevention of IRI and significantly prolonged allograft survival. Donor simvastatin treatment inhibited allograft microvascular RhoA GTPase pathway activation, whereas methylprednisolone prevented activation of innate immune response and mRNA expression of hypoxia-inducible factor-1α and its multiple target genes.

CONCLUSIONS

Our results show that donor treatment in combination with simvastatin and methylprednisolone prevents IRI and has beneficial effect on allograft survival in rat cardiac allografts. Minimizing microvascular injury and the activation of innate immunity may offer a novel therapeutic strategy to expand the donor pool and furthermore improve the function of the marginal donor organs.

Effect of cytokine hemoadsorption on brain death-induced ventricular dysfunction in a porcine model

OBJECTIVE

In an effort to expand the cardiac donor pool, we tested the hypothesis that hemoadsorption of cytokines attenuates brain death-induced ventricular dysfunction.

METHODS

Eighteen Yorkshire pigs (50-60 kg) were instrumented with a left ventricular conductance catheter. Cytokine expression, preload recruitable stroke work, and the diastolic relaxation constant tau were measured at baseline and at hourly intervals for 6 hours after induction of brain death by intracranial balloon inflation (brain death, n = 6) or sham operation (control, n = 6). In a third group (brain death + hemoadsorption, n = 6), 3 hours after induction of brain death, animals were placed on an extracorporeal circuit containing a cytokine-hemoadsorption device for the remaining 3 hours of the experiment. Myocardial water content was measured after the animals were killed.

RESULTS

Six hours after induction of brain death, tumor necrosis factor and interleukin-6 were highest in the brain death group (106 ± 13.1 pg/mL and 301 ± 181 pg/mL, respectively), lowest in controls (68.3 ± 8.55 pg/mL and 37.8 ± 11 pg/mL, respectively), and intermediate in the brain death + hemoadsorption group (81.2 ± 35.2 pg/mL and 94.6 ± 20 pg/mL, respectively). Compared with controls, preload recruitable stroke work was significantly reduced in the brain death group 4 hours after the induction of brain death and was 50% of baseline by 5 hours. In the brain death + hemoadsorption group, preload recruitable stroke work was relatively preserved at 80% of baseline at similar time points. Tau remained unchanged in the control and brain death + hemoadsorption groups, whereas in the brain death group it was significantly elevated versus baseline 5 (139.3% ± 21.5%) and 6 (172% ± 16.1%) hours after induction of brain death. Myocardial water content was significantly greater in the brain death group than in the other 2 groups.

CONCLUSIONS

Hemoadsorption of cytokines using an extracorporeal circuit attenuates brain death-induced ventricular dysfunction in a porcine model. Improvement in function generally correlates with trends in cytokine expression, but this relationship requires further investigation.

Brain death induced by cerebral haemorrhage - a new porcine model evaluated by CT angiography

BACKGROUND

Brain death and complications to brain death affects the function of organs in the potential donor. Previous animal models of brain death have not been able to fully elucidate the mechanisms behind this organ dysfunction, and none of the available animal models mimic the most common insult prior to brain death: intracerebral haemorrhage. The objective of this study was to develop a large animal model of brain death based on a controlled intracerebral haemorrhage and verified by computerised tomographic angiography (CTA).

METHODS

Twenty pigs (range: 26.6-31.2 kg) were randomised to brain death or control. Brain death was induced by infusion of blood through a stereotaxically placed needle in the internal capsule. Brain death was confirmed by the measured intracranial pressure (ICP), lack of corneal and pupillary light reflexes, and atropine test. CTA was performed 120-180 min after brain death. The pigs were observed for 8 h after brain death.

RESULTS

Brain death was declared when the ICP exceeded mean arterial pressure after a median of 36 min (range: 28-51 min). Significant increases in heart rate, and mean arterial pressure (MAP) were followed by a steep decrease. With fluid therapy, the animals demonstrated haemodynamic stability. Reflexes disappeared, and atropine did not induce an increase in heart rate in the brain dead animals. CTA confirmed loss of cerebral circulation.

CONCLUSION

This study offers a standardised, clinically relevant porcine model of brain death induced by a haemorrhagic attack. Brain death was verified by the disappearance of corneal and pupil reflex, atropine test, and CTA.

Effects of brain death on organ quality and transplant outcome

The inferiority of organs from brain dead donors is reflected by impaired graft survival and patient outcome. Brain death effects hemodynamic stability, hormonal changes, and neuroimmunologic effects and unleashes a cascade of inflammatory events. Despite considerable efforts in experimental and clinical research, most of the mechanisms linked to brain death are only appreciated on a descriptive level. This overview presents our current understanding of the pathophysiology and consequences of brain death on organ injury and summarizes available therapeutic interventions.

Endocrine changes in brain death and transplantation

Following brain death (BD) many hormonal changes occur. These include an increase and then a fall in the levels of circulating catecholamines, reduced levels of anti-diuretic hormone and cortisol as well as alterations in the hypothalamic-pituitary thyroid axis consistent with the non-thyroidal illness syndrome. In an era when the numbers of potential recipients listed for transplantation are greater than the number of donors, with an increasing donor age, a detailed knowledge of the endocrine changes and pathophysiological consequences of these is essential to optimise the management of the brain-stem dead organ donor. There still remains significant debate as to whether hormone replacement therapy to correct the observed changes is beneficial.

Contribution of Toll-like receptor activation to lung damage after donor brain death

INTRODUCTION

Donor brain death is the first injurious event that can produce inflammatory dysfunction after pulmonary transplantation. This study was designed to determine whether stimulation of the toll-like receptor (TLR) system contributes to the changes produced by brain death.

MATERIALS AND METHODS

Rats were repeatedly treated with specific agonists for TLR4 or TLR2/6 to desensitize these receptors. Brain death was then induced by inflation of a balloon catheter within the extradural space. Mean arterial pressure changes and inflammatory markers were measured serially by protein and mRNA analysis.

RESULTS

Both desensitizing pretreatments prevented the neurogenic hypotension (P<0.001) and metabolic acidosis (P<0.001) observed in control animals after brain death. These treatments also reduced the levels of tumor necrosis factor-α and CXCL1 in serum and bronchoalveolar lavage fluid, although desensitization of TLR4 produced a greater inhibition than desensitization of TLR2. Desensitization of TLR4 also reduced (P<0.05) expression of the adhesive integrin CD11b on blood neutrophils after brain death. Examination of mRNA levels in lung tissue 5 hr after brain death showed that desensitization of TLR4 limited the expression of interferon (IFN)-γ, IFNβ, and CXCL10, whereas desensitization of TLR2/6 reduced only the expression of IFNγ.

CONCLUSION

These results indicate that activation of TLR signaling pathways can contribute to the lung damage produced by brain death; this may increase subsequent graft injury after transplantation.

Controversial points in organ donor management

There are still many controversial aspects regarding which method is best for managing organ donors to prevent, lessen, or even reverse the organ alterations associated with brain death. Fundamental aspects are the management of an adequate perfusion pressure, hormone restoration, and opposition of the inflammatory state associated with brain death. Once volume has been normalized, it is necessary to administer vasoactive drugs, including catecholamines to re-establish the loss of sympathetic tone at the vascular and myocardial level. It is impossible to define the ideal or maximal catecholamine dose because it depends on the donor's vascular tone, vascular reactivity, and pharmacokinetic variability characteristic of critical patients, particularly organ donors. To control early onset of diabetes insipidus, it is necessary to administer desmopressin. At present there are insufficient clinical studies to show the usefulness of triiodothyronine. Furthermore, due to its limited availability, elevated cost, and probable side effects, the use of this hormone is not justified. More importance is being given to the negative influence of the inflammatory state associated with brain death, which has repercussions on organ viability and probably influences the prevalence of rejection episodes. Meanwhile in organ donor management, we recommend the use of 15 mg/kg of methylprednisolone as soon as possible. Contrary to triiodothyronine, the potential benefit of its immunomodulatory effects, its low cost, and the absence of major side effects justify this recommendation.

Mechanism of the protective effects of N-acetylcysteine on the heart of brain-dead Ba-Ma miniature pigs

BACKGROUND

Severe stress response induced by brain death leads to a marked increase in the expression of inflammatory cytokines regulated by nuclear factor-kappaB (NF-kappaB). N-acetylcysteine may inhibit activation of the NF-kappaB pathway. This study examined the expression of NF-kappaB in the hearts of brain-dead Ba-Ma miniature pigs and the protection potential of N-acetylcysteine.

METHODS

Ba-Ma miniature pigs were randomized into 3 groups: control group (Group C), N-acetylcysteine-free group (Group B), and N-acetylcysteine treatment group (Group N). At 6, 12, and 24 hours after the initial brain death, serum cardiac troponin-T (cTnT), tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and IL-6 were examined. Heart tissue was taken 24 hours after the initial brain death. Structural changes of the heart and the expression of NF-kappaB were analyzed.

RESULTS

At 6 hours after the initial brain death, serum levels of cTnT, TNF-alpha, IL-1beta, and IL-6 in Groups B and N began to increase. Levels in Group B increased more dramatically than in Group N. At 24 hours, cardiocyte damage was documented, but the damage in Group N was less severe than that in Group B. The expression of NF-kappaB in Groups B and N increased, and expression in Group B increased more sharply than in Group N.

CONCLUSIONS

N-acetylcysteine can alleviate both structural and functional injury of the heart during brain death, which might be related to the inhibition of NF-kappaB expression and decreasing release of inflammatory mediators.

[Hormone modulation of organ donor. Utility of the steroids]

Recently, the work group made up of the National Transplant Organization (Organización Nacional de Trasplantes, ONT), Spanish Society of Intensive, Critical Medicine and Coronary Units (Sociedad Española de Medicina Intensiva, Crítica y de Unidades Coronarias, SEMICYUC) and other Scientific Societies have recommended using 15 mg/kg of methyl prednisolone during the management of lung donors after brain death. This recommendation is based on descriptive and retrospective studies. However, the review of different experimental and clinical studies also suggests a potential benefit of using steroids in either thoracic or abdominal organ donors during management strategies. In brain death management, early steroid administration may decrease cytokine production and also may prevent alterations induced by proinflammatoy mediators, stabilize cell membranes, reduce expression of cell surface adhesion molecules and avoid lipid peroxidation after the ischemic period. This could be beneficial in increasing number and quality of organs harvested and in decreasing rejection episodes after transplant. It would be very recommendable to carry out prospective and comparative studies to demonstrate these potential utilities. Meanwhile and knowing the deleterious effects of inflammatory activity arising during and after brain death, we recommend using 15 mg/kg of methyl prednisolone in the organ donor management, as soon as possible. The potential benefit of its immunomodulation effects, its low cost and the absence of major side effects can justify this recommendation.

Systemic inflammation in the brain-dead organ donor

Brain death itself impairs organ function in the potential donor, thereby limiting the number of suitable organs for transplantation. In addition, graft survival of kidneys obtained from brain-dead (BD) donors is inferior to that of kidneys obtained from living donors. Experimental studies confirm an inferior graft survival for the heart, liver and lungs from BD compared with living donors. The mechanism underlying the deteriorating effect of brain death on the organs has not yet been fully established. We know that brain death triggers massive circulatory, hormonal and metabolic changes. Moreover, the past 10 years have produced evidence that brain death is associated with a systemic inflammatory response. However, it remains uncertain whether the inflammation is induced by brain death itself or by events before and after becoming BD. The purpose of this study is to discuss the risk factors associated with brain death in general and the inflammatory response in the organs in particular. Special attention will be paid to the heart, lung, liver and kidney and evidence will be presented from clinical and experimental studies.

Does brain death induce a pro-inflammatory response at the organ level in a porcine model?

BACKGROUND

Organs from brain-dead donors have a poorer prognosis after transplantation than organs from living donors. A possible explanation for this is that brain death might initiate a systemic inflammatory response, elicited by a metabolic stress response or brain ischemia. The aim of this study was to investigate the effect of brain death on the cytokine content in the heart, liver, and kidney. In addition, the metabolic and hemodynamic response caused by brain death was carefully registered.

METHODS

Fourteen pigs (35-40 kg) were randomized into two groups (1) eight brain-dead pigs and (2) six pigs only sham operated. Brain death was induced by inflation of an epidurally placed balloon. Blood samples for insulin, glucose, catecholamine, free fatty acids (FAA), and glucagon were obtained during the experimental period of 360 min. At the conclusion of the experiment, biopsies were taken from the heart, liver, and kidney and were analyzed for cytokine mRNA and proteins [tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-6, and IL-10).

RESULTS

We found a dramatic response to brain death on plasma levels of epinephrine (P=0.004), norepinephrine (P=0.02), FAA (P=0.0001), and glucagon (P=0.0003) compared with the sham group. There was no difference in cytokine content in any organ between the groups.

CONCLUSION

In this porcine model, brain death induced a severe metabolic response in peripheral blood. At the organ level, however, there was no difference in the cytokine response between the groups.

The effects of hormone resuscitation on cardiac function and hemodynamics in a porcine brain-dead organ donor model

We compared the effects of hormone resuscitation (HR) with a norepinephrine-based protocol on cardiac function, hemodynamics and need for vasopressor support after brain death in a porcine model. Following brain death induction, animals were treated with norepinephrine and fluids for 3 h. In the following 3 h, they continued on norepinephrine and fluids (control) or received additional HR (triiodothyronine, methylprednisolone, vasopressin, insulin). Data were collected pre-brain death, 3 and 6 h post-brain death. At 6 h, median norepinephrine use was higher in controls (0.563 vs. 0 microg/kg/min; p < 0.005), with 6/8 HR animals weaned off norepinephrine compared with 0/9 controls. Mean arterial pressure was higher in HR animals at 6 h (74 +/- 17 vs. 54 +/- 14 mmHg; p < 0.05). Cardiac contractility was also significantly higher in HR animals at 6 h (stroke work index 1.777 vs. 1.494). After collection of 6 h data, all animals were placed on the same low dose of norepinephrine. At 6.25 h, HR animals had higher stroke work (3540 +/- 1083 vs. 1536 +/- 702 mL.mmHg; p < 0.005), stroke volume (37.2 +/- 8.2 vs. 21.5 +/- 9.8 mL; p < 0.01) and cardiac output (5.8 +/- 1.4 vs. 3.2 +/- 1.2 L/min; p < 0.005). HR in a porcine model of brain death reduces norepinephrine requirements, and improves hemodynamics and cardiac function. These results support the use of HR in the management of the brain-dead donor.

Beta-adrenergic receptor antagonism preserves myocardial function after brain death in a porcine model

BACKGROUND

Cardiac dysfunction after brain death decreases the already limited number of potential donors for cardiac transplantation. Acute beta-adrenergic receptor (betaAR) desensitization after the brain death-associated catecholamine surge is an important mechanism. We hypothesized that acute betaAR antagonism could improve myocardial function after brain death by preserving betaAR signaling.

METHODS

Pigs were randomly assigned to three study groups (n = 5): sham; brain death; and brain death with betaAR antagonist (200 microg/kg/min esmolol), 30 minutes before brain death until 45 minutes after brain death. Functional data were collected for 6 hours after brain death and tissues procured.

RESULTS

Compared with baseline, pre-load recruitable stroke work (PRSW), a pre-load-independent measure of systolic function (21.4 +/- 7.5 vs 43.3 +/- 6.8, slope of regression line during vena caval occlusion, p < 0.001), diastolic function (Tau, 101 +/- 54.7 vs 36.4 +/- 5.4 ms, p = 0.03) and systemic oxygen delivery (151 +/- 79.7 vs 298 +/- 78.7 ml/min, p < 0.001) deteriorated in untreated animals at 6 hours after brain death. In contrast, betaAR antagonist maintained baseline systolic function (PRSW, 37.8 +/- 5.6 vs 38.2 +/- 4.7, slope of regression line during vena caval occlusion, p = 0.92), diastolic function (Tau, 32.6 +/- 5.1 vs 48.5 +/- 28.3 ms, p = 0.57) and oxygen delivery (427 +/- 116 vs 397 +/- 98.8 ml/min, p = 0.36) at 6 hours after brain death. betaAR antagonist preserved betaAR signaling, as demonstrated by similar left ventricular (LV) basal (55.4 +/- 32.8 vs 58.8 +/- 10.9 pmol/mg/min, p = 0.40) and isoproterenol-stimulated (125 +/- 70.5 vs 124 +/- 52.0 pmol/mg/min, p = 0.49) adenylate cyclase activity at 6 hours after brain death, upon comparing betaAR antagonist and sham treatment groups. Both LV basal and isoproterenol-stimulated adenyl cyclase activity were higher with betaAR antagonist (25.9 +/- 4.8 pmol/mg/min, p = 0.03) than with untreated brain death (55.6 +/- 17.3 pmol/mg/min, p = 0.02).

CONCLUSIONS

Beta-adrenergic receptor antagonism before brain death preserves cardiac function by preventing betaAR desensitization. This therapy in potential donors might increase the number of organs available for transplantation.

Glucocorticoids Alter the Balance Between Pro- and Anti-inflammatory Mediators in the Myocardium in a Porcine Model of Brain Death

BACKGROUND

Cardiac dysfunction after brain death (BD) limits donors for cardiac transplantation. Glucocorticoids ameliorate brain death-induced donor heart dysfunction. We hypothesized that glucocorticoid therapy alleviates myocardial depression through altering the balance between pro- and anti-inflammatory mediators via the nuclear factor-kappaB (NF-kappaB)/inhibitor of kappaB-alpha (IkappaBalpha) pathway and/or by preserving beta-adrenergic receptor (betaAR) signaling in the heart.

METHODS

Crossbred pigs (25 to 35 kg) were randomly assigned to the following groups (n = 5/treatment): sham (Group 1); BD (Group 2); and BD with glucocorticoids (30 mg/kg methylprednisolone), either 2 hours before (Group 3) or 1 hour after BD (Group 4). Tumor necrosis factor-alpha (TNF-alpha) levels were measured in plasma at baseline and 1 hour and 6 hours after BD. Protein levels were measured in left ventricular homogenates procured 6 hours after BD.

RESULTS

Pro-inflammatory proteins (TNF-alpha) and interleukin-6 were lower in Group 3 and Group 4 compared with Group 2 at 6 hours after BD (p < 0.01). Intracellular adhesion molecule-1 was also lower in Group 4 compared with Group 2 (p = 0.001). Interleukin-10, an anti-inflammatory mediator, was lower in Group 4 than in Group 2 (p < 0.001), but not different between Groups 2 and 3. At 6 hours after BD, neither NF-kappaB activity nor basal adenylate cyclase activity differed between Groups 3 and 4 compared with Group 2.

CONCLUSIONS

Glucocorticoids maintained myocardial function and shifted the balance of pro- and anti-inflammatory mediators after BD. The mechanisms by which glucocorticoids preserve myocardial function, however, do not appear to involve the NF-kappaB pathway or betaAR signaling.